When should Republicans jump ship?

"History will judge us," Senate Minority Leader Chuck Schumer, D-N.Y., said on the Senate floor recently, arguing for impeaching President Donald Trump. It's a line we hear a lot, pregnant with ominous implications. This is no time for the usual partisan antics, the warning intimates. We must rise to the Call of History. But how can we know what history will say about Trump's prosecutors and defenders before we get there?

It's not easy to know what history will say about anything. Reputations and judgments fluctuate. Not long ago, most historians would have thought it laughable to honor Dwight Eisenhower with a memorial on the Mall, and few would have considered Thomas Jefferson more a villain than a hero because he owned slaves. All George W. Bush had to do was sit idly by and let Donald Trump govern to see his own image improve. To appeal to the verdict of history, as if it were stable and discernible, is presumptuous. It can also be disingenuous, a pretense for the real argument — that your antagonists are making a political choice you don't like.

Still, people return to this notion for a reason: It acknowledges the potentially high stakes of any political action — how a single vote or decision can loom large in someone's legacy when the day of reckoning finally comes. It appeals to transcendent ideals that may be obscured by the fervor of the moment; sometimes these coalesce crisply over time, making right and wrong seem obvious and incontestable in retrospect. When, for example, a dying Sen. John McCain went to the well of the Senate to give his thumbs-down on the gutting of Obamacare, he knew this was an act he'd be remembered for.

Today, as a president awaits a decision about his impeachment, those who caution his defenders to beware posterity are probably thinking about Watergate. They suggest that the partisans and ideologues who stood fast by Richard Nixon despite mounting evidence of his criminality forever sullied their reputations. "If Republicans are willing to go along with this, it is going to change our history," Carl Bernstein, one of the Washington Post reporters who helped break the Watergate story, told CNN recently. "Because Republicans became the heroes in Watergate who finally said, 'We cannot tolerate a corrupt president who undermines our electoral system.' " As the podcaster Steve Almond put it, "What the country yearns for right now is another [Barry] Goldwater, a leader in the Senate with national name recognition and conservative bona fides" — who famously broke with Nixon during Watergate and helped turn Republican opinion against the president.

The trouble is, history doesn't always speak with one voice. Not all of Nixon's bitter-enders suffered. Several lived down their apologetics and went on to distinguished careers or great popularity. So Democrats can't confidently claim that defending Trump against impeachment will earn permanent ignominy for Republicans.

But the Watergate saga does tell us this much: Those loyalists who abandoned Nixon early, when it mattered — who stood up for principle over party, for integrity over professional advancement, before Nixon was politically doomed — are remembered and praised for their courage. Men such as Sen. Lowell Weicker and Rep. William Cohen cemented their legacies as honorable public servants and were lionized for the rest of their lives. Those who waited to see the writing on the wall (Republicans in Congress, administration officials who wanted to serve the national interest but lacked the courage to break with their boss) left their fates to chance. Many of them are now remembered solely for sticking by a man who abused the power of his office — if, that is, they are remembered at all.

The parallels between 1974 and 2019 are inexact. Republicans back then were much more independent-minded; many broke with their president not just during the impeachment process but well before that, on ordinary legislative matters. According to Congressional Quarterly's statistics, in the early 1970s the parties stuck together on key votes between 60 and 65 % of the time; these days it is upward of 90 percent of the time. Back then, the GOP included liberals and moderates who had no ideological affinity for the president and openly voiced doubts about Nixon's honesty. When Nixon left office, most of his party-mates tried to get on the "right side of history" by publicly disavowing him. Today, with a right-wing mediasphere where the likes of Rush Limbaugh and Fox News constantly reinforce White House talking points, it's almost impossible to imagine that happening.

House Judiciary Committee Republicans Joseph Maraziti of New Jersey and Wiley Mayne of Iowa, who voted no on all three impeachment counts, also lost their re-election campaigns. Both men went back to practicing law locally; Maraziti failed several times to regain political office.

Reps. Charles Sandman of New Jersey, Charles Wiggins of California and David Dennis of Indiana were among Nixon's most ardent defenders on the Judiciary Committee. There, all three voted against the impeachment counts. Shortly after that vote, however, upon hearing the "smoking gun" tape that captured Nixon plotting the Watergate coverup, all concluded they'd been lied to and reversed themselves, saying they would now support impeachment for obstruction of justice in the event of a House floor vote. Nixon resigned before that could happen. Nevertheless, Sandman and Dennis lost re-election.

None of these men has been well remembered. All of their obituaries led with the fact that they defended Nixon. That decision became the headline of their entire lives.

And well before that, the 1974 midterms were a disaster for the Republicans. The Democrats gained 49 seats in the House, to reach a 291-to-144 majority, and four seats in the Senate, for an effective 61-to-37 majority.

If only history were so neat and tidy. Six Republicans who voted against impeachment survived, including Wiggins and Mississippi's Trent Lott, who went on to be Senate majority leader a quarter-century later and will be much better remembered for that role. Supporting Nixon was also less damaging to the president's White House spin doctors, like Pat Buchanan, John McLaughlin and Ben Stein, who went on to extraordinarily successful television careers. They marketed their pugnacious styles of argument to help define the TV news culture of the 1980s and 1990s.

For Bush, the emergence of proof that the president had been lying to him "shattered [his] trust in Nixon," his son George W. Bush later wrote, and the elder Bush let it be known that in the final days he called on the president to resign. "The man is amoral," he noted coldly in his diary. Dole and Bush both later won their party's presidential nomination, and one became president.

Because history has sometimes forgiven Nixon's apologists, we can't say for certain that it will indelibly stain Trump's boosters. Some will have opportunities to reshape their legacies. Still, if Trump is impeached — or if he goes down in history as having degraded our democracy and its norms — we can make some educated guesses about what posterity will say about those who desert him. In the 45 years since Nixon's resignation, the consensus that his impeachment was warranted has held strong, and the Republicans who led the way in criticizing him are now remembered as courageous freethinkers.

One liberal Republican on the Senate Watergate Committee, Lowell Weicker of Connecticut, questioned its witnesses fiercely — at a time when the ranking Republican, Howard Baker of Tennessee, was still carrying Nixon's water. "I would get flipped the bird all the time, whether it was on the streets or in the car, for the role that I was playing," Weicker later recalled. "After Watergate was over, then the needle goes all the way the other way, and I've got huge favorability ratings." Weicker, who left the GOP, later served as Connecticut's governor.

Republican Edward Brooke of Massachusetts, the first African-American senator since Reconstruction, called on Nixon to resign after the "Saturday Night Massacre," in which Attorney General Elliot Richardson and his No. 2, William Ruckelshaus, quit rather than comply with Nixon's order to fire the Watergate special prosecutor. Brooke would later receive a Presidential Medal of Freedom and have a Boston courthouse named in his honor.

Richardson's resignation has been seen as an act of principle and "lauded as a special moment of integrity and rectitude that secured him a place in the nation's history," his New York Times obituary said. He was often sought out for roles requiring moral authority, such as serving as the chief monitor for Nicaragua's 1990 elections after the fall of the repressive Sandinista government. President Bill Clinton eulogized him, saying that he "put the nation's interests first even when the personal cost was very high."

In April 1973, Barry Goldwater, tribune of the far right, grumbled that Watergate was "beginning to smell like Teapot Dome." Once reviled on the left as a self-described extremist, Goldwater enjoyed nostalgic reminiscences even from liberals in the years before his death — with his courage in defying Nixon playing an important role. New York Sen. James Buckley, an archconservative and brother of journalist William F. Buckley, demanded Nixon's resignation from the Senate floor in early 1974. Sen. Buckley, though less-remembered now, went on to a slot on the prestigious U.S. Court of Appeals for the D.C. Circuit. He was able to win Senate confirmation by a vote of 84 to 11 in part because his independence during Watergate convinced Democrats that he would not be a conservative ideologue on the bench.

In the House, too, many Republicans put country above party. Judiciary Committee members William Cohen of Maine and Tom Railsback of Illinois backed impeachment early in the summer of 1974, making it safe for their fellow Republicans to get on board. Of the 17 Republicans on the Judiciary Committee who had to vote on impeachment, seven ultimately supported at least one article. Cohen in particular went on to a distinguished Senate career, played a major role in investigating the Iran-contra affair and served as defense secretary under Clinton.

Railsback became a lobbyist, but even today, his boldness is remembered and held up as a contrast to House Republicans' unwillingness to cross Trump. "Where's our Bill Cohen? Where's our Hamilton Fish? Where's our Tom Railsback?" Rep. Zoe Lofgren, D-Calif., asked earlier this year. (Fish, a Republican from western New York, also voted for the impeachment charges in committee.)

Finally, to ensure that the system worked, it took the cooperation of the Supreme Court — including the Nixon-appointed justices Warren Burger, Lewis Powell and Harry Blackmun — in handing down a unanimous decision requiring the president to comply with subpoenas for his tapes. (A fourth Nixon appointee and former Nixon staffer, William Rehnquist, recused himself.) The 8-to-0 decision is still taught as a classic case of justices putting the law above their political leanings.

In 1955, Sen. John F. Kennedy wrote "Profiles in Courage," a study of senators who, in his opinion, had defied intense pressure from their constituents and party leaders in taking principled positions. Over time, not all of Kennedy's judgments have held up. (Edmund Ross, for example, whom he praised for saving Andrew Johnson from impeachment in 1868, turns out to have been something of a scoundrel.) But the concept Kennedy bequeathed to our political understanding — the valor, in difficult times, of putting country before party — was evident during Watergate and endures today.